Cooling towers transfer heat from a fluid to the atmosphere through evaporation. One type of cooling tower, referred to as a mechanical draft cooling tower, provides cooled water for air conditioning, manufacturing, and power generation systems. For example, a cooling tower for use with a heating ventilation and air conditioning system (“HVAC”) may receive heated water from a chiller or other HVAC unit, transfer heat from the water to the atmosphere, and return cooled water to the chiller.
FIG. 8 illustrates an exemplary cooling tower 10, which includes a housing 14, a fluid input conduit 18, a fluid output conduit 22, a basin 26, fill material 30, a motor 34, and a fan 38. The housing 14 defines an internal chamber having an airflow input 42 and an airflow output 46. The motor 34 rotates the fan 38, which draws air into the chamber through the inlet 42 and forces air out of the chamber through the outlet 46. The fluid input 18 directs heated fluid, typically water from another portion of the HVAC system, into the chamber. Nozzles 50 terminate the fluid input 18 and the heated water 54 sprays out of the nozzles and onto the fill material 30. The fill material 30 has a large total surface area to promote evaporation of the water. Typical fill material 30 may include sheets of a thin material separated by a narrow distance through which the heated water trickles downward against the airflow generated by the fan 38. A portion of the water moving through the fill material 30 evaporates and extracts heat from the fill material and the air within the chamber. The remaining portion of the water trickles through the cooled fill material and falls into the basin 26. The water collected by the basin 26 has a temperature less than the temperature of the heated water 54. The water moves from the basin 26 to the output 22, which pipes the water to other portions of the HVAC system.
Operation of the cooling tower causes the air in the chamber to become laden with moisture. In particular, the air within the chamber and the air surrounding the housing may have a relative humidity of approximately 100%. The moisture laden air may have adverse effects on some mechanical and electrical components positioned within the chamber. For example, as shown in FIG. 8, the cooling tower 10 includes the electrical motor 34 positioned within the chamber. Accordingly, the cooling tower 10 exposes the electrical motor to mist and water vapor each of which subject the motor 34 to moisture damage. In particular, the stator windings of the motor 34 may become corroded, oxidized, or otherwise damaged as a result of the extremely humid and damp operating environment of the cooling tower 10.
Methods of operating an HVAC system may also increase the risk of moisture damage to the electrical motors associated with cooling towers. Some HVAC systems include a single cooling tower with a cooling capacity equal to or exceeding a maximum required cooling capacity. These HVAC systems activate the singular cooling tower each time the system requires the effects of the cooling tower. Residual heat from the electrical motor may evaporate some of the moisture surrounding the stator winding; nonetheless, regularly exposing the motor to the damp and humid operating environment contributes to moisture damage. Other HVAC systems include numerous cooling towers, which provide a combined cooling capacity equal to or exceeding the required cooling capacity. These HVAC systems may activate only the cooling towers needed to generate the required cooling capacity, while the other cooling towers remain inactive for potentially months at a time. The electrical motors of the regularly activated cooling towers benefit from the moisture eliminating effects of the residual motor heat, but remain susceptible to moisture damage as a result of the frequent exposure to the damp and humid operating environment. The electrical motors of the infrequently utilized cooling towers, are exposed to the damp and humid operating environment generated by the regularly activated cooling towers, and may be even more susceptible to moisture damage because the electrical motors of the infrequently utilized cooling towers do not regularly benefit from the residual motor heat. Accordingly, a need continues for further developments in the area of moisture protection for the electrical motors associated with cooling towers utilized in HVAC systems.